This invention relates to a direct injected internal combustion engine and more particular to an improved injection control for such an engine.
There continues to be a demand for improved performance in internal combustion engines. Although alternative power sources have been considered, internal combustion engines still offer a very efficient and environmentally friendly supply of power. However, in many applications for engines, such as in powering vehicles, the engine is required to run over widely varying load and speed ranges. It is very difficult to ensure good performance, maximum fuel economy, and effective emission control under all such running conditions.
Various devices have been proposed so as to improve the performance of an engine and also to improve its flexibility. In order to obtain better combustion control, it has been proposed to employ direct cylinder injection. With direct cylinder injection, the fuel is injected directly into the combustion chamber of the engine. This has a number of advantages.
One of the important advantages of using direct cylinder injection is that it lends itself to achieving stratification in the combustion chamber. A conventional engine has a homogeneous fuel/air mixture in the entire combustion chamber at the time of combustion, regardless of the load. This means that the cylinder is overcharged with fuel under most running conditions.
Thus, attempts to provide what is referred to as "lean burn" have been resorted to. By running on a lean burn condition, the entire combustion chamber is not charged with a homogeneous, stoichiometric fuel/air mixture. If there can be provided a stoichiometric patch of fuel at the spark gap at the time of firing, the entire cylinder need not be charged with a stoichiometric mixture. This has obvious advantages from the point of not only fuel economy, but also exhaust emission control.
However, in order to achieve this stratification, it is necessary to have the combustion chamber appropriately configured and to have the fuel injector position so as to spray into the optimum position to achieve stratification. This problem is particularly acute when utilizing multiple valves and overhead cam shafts. Also there are times when stratification is either not desirable or the degree of stratification should be limited.
Therefore it is a principle object of this invention to provide an improved fuel injection position for an engine having direct injection and wherein stratification can be achieved and its degree controlled.